An optoelectronic component, for example an organic light emitting diode (OLED), includes at least two electrodes and an organic functional layer system therebetween.
Present-day OLEDs have an aging behavior, i.e. with constant operating current the forward voltage rises as the operating period increases, as a result of which the light intensity decreases.
In order to slow down the fall in light intensity, the operating current could be slowly increased in accordance with the age. For this purpose, however, the luminance should be measured over the entire operating period or, alternatively, a variable approximately proportional to the fall in luminance should be measured. The measurement of the luminance is usually realized by a light sensor, but the measured luminance is influenced by ambient light.
Furthermore, in the case of a fault of an OLED, for example a short circuit (short), local overheating (hotspot) or in incorrect operation, for example polarity reversal or application of an excessively high operating current, the OLED becomes very hot and can become dangerous, for example rupture, or cause a fire or combustion upon contact. Switching off the OLED in a timely manner could afford protection against overheating, but this necessitates measuring the temperature of the OLED over the entire operating period.
One conventional method for measuring the temperature of an OLED involves fixing external temperature sensors, for example temperature probes, in the outer side of an OLED, for example by thermoelements being adhesively bonded on an optically inactive OLED surface by thermally conductive paste. However, this method may locally influence the heat flow at the OLED surface and, for example, pass on a corrupted measured temperature to the regulating device of the operating current of the OLED. At the same time, by this measuring method, the temperature is determined only at points and only at the surface of the OLED. Furthermore, the adhesively bonded temperature element may have a disturbing effect on the overall esthetic impression of the OLED.
Furthermore, coupling a temperature sensor and/or a light sensor to an OLED is susceptible to errors, for example in terms of the accuracy of the adhesive thickness in the case of adhesively bonded sensors and the positioning of the sensors.